Benomyl Tolerance of Ten Fungi Antagonistic to Plant-parasitic Nematodes

Abstract

Ten strains of fungi were tested for tolerance to the fungicide benomyl. Verticillium chlamydosporium strain 2 did not grow in the presence of benomyl; Drechraeria coniospora strains 1 and 2 and Chaetomium sp. tolerated only 0.1 [mu]g benomyl/ml medium; Acremonium bacillisporum, an unidentified fungus, and Phoma chrysanthemicola uniformly grew at 1 [mu]g/ml, but some hyphae grew at higher benomyl concentrations; Fusarium sp. tolerated 475 [mu]g/ml, but some hyphae grew on medium amended with 1,000 [mu]g/ml; Verticilliura lecanii and V. chlamydosporium strain 1 routinely tolerated 1,000 [mu]g/ml. Fungi generally grew more slowly at higher than at lower benomyl concentrations. Strains with elevated tolerance to benomyl were selected from Acremonium bacillisporum, Drechmeria coniospora, Fusarium sp., and an unidentified fungus. These strains retained the increased tolerance after repeated transfers on unamended medium. Key words: benomyl, biological control, fungicide effect, fungus, Heterodera glycines, nematode, nontarget organism, soybean cyst nematode.